SNI.YAML

NAME

sni.yaml - Traffic Server sni rules configuration file

DESCRIPTION

This file is used to configure aspects of TLS connection handling for both inbound and outbound connections. With the exception of host_sni_policy (see the description below), the configuration is driven by the SNI values provided by the inbound connection. The file consists of a set of configuration items, each identified by an SNI value (fqdn). When an inbound TLS connection is made, the SNI value from the TLS negotiation is matched against the items specified by this file and if there is a match, the values specified in that item override the defaults. This is done during the inbound connection processing; some outbound properties can be overridden again later, such as via remap.config or plugins.

By default this is named sni.yaml. The filename can be changed by setting proxy.config.ssl.servername.filename. This file is loaded on start up and by traffic_ctl config reload if the file has been modified since process start.

The configuration file is YAML-based. After parsing the configuration, a list of tables will be the result. Each table is a set of key / value pairs that create a configuration item. This configuration file accepts wildcard entries. To apply an SNI based setting on all the server names with a common upper level domain name, the user needs to enter the fqdn in the configuration with a *. followed by the common domain name. (*.yahoo.com for example).

For some settings, there is no guarantee that they will be applied to a connection under certain conditions. An established TLS connection may be reused for another server name if itâs used for HTTP/2. This also means that settings for server name A may affects requests for server name B as well. See https://daniel.haxx.se/blog/2016/08/18/http2-connection-coalescing/ for a more detailed description of HTTP/2 connection coalescing.

Pre-warming TLS Tunnel

Client verification, via verify_client, corresponds to setting proxy.config.ssl.client.certification_level for this connection as noted below.
NONE -- 0

Do not request a client certificate, ignore it if one is provided.

MODERATE - 1

Request a client certificate and do verification if one is provided. The connection is denied if the verification of the client provided certificate fails.

STRICT - 2

Request a client certificate and require one to be provided and verified. If the verification fails the failure is logged to diags.log and the connection is denied.

Upstream (server) verification, via verify_server_policy and verify_server_properties, is similar to client verification except there is always an upstream certificate. This is equivalent to setting proxy.config.ssl.client.verify.server.policy and proxy.config.ssl.client.verify.server.properties for this connection.

verify_server_policy specifies how Traffic Server will enforce the server certificate verification.
DISABLED

Do not verify the upstream server certificate.

PERMISSIVE

Do verification of the upstream certificate but do not enforce. If the verification fails the failure is logged in diags.log but the connection is allowed.

ENFORCED

Do verification of the upstream certificate. If verification fails, the failure is logged in diags.log and the connection is denied.

In addition verify_server_properties specifies what Traffic Server will check when performing the verification.

NONE

Do not check anything in the standard Traffic Server verification routine. Rely entirely on the TS_SSL_VERIFY_SERVER_HOOK for evaluating the origin's certificate.

SIGNATURE

Check the signature of the origin certificate.

	NAME		Verify that the SNI is in the origin certificate.
	ALL		Verify both the signature and the SNI in the origin certificate.

If tunnel_route is specified, none of the certificate verification will be done because the TLS negotiation will be tunneled to the upstream target, making those values irrelevant for that configuration item. This option is explained in more detail in SNI Routing.

EXAMPLES

Disable HTTP/2 for no-http2.example.com.

sni:
- fqdn: no-http2.example.com
http2: off

Require client certificate verification for foo.com and any server name ending with .yahoo.com. Therefore, client request for a server name ending with yahoo.com (e.g., def.yahoo.com, abc.yahoo.com etc.) will cause Traffic Server require and verify the client certificate.

For foo.com, if the user agent sets the host header to foo.com but the SNI to some other value, Traffic Server will warn about the mismatch but continue to process the request. Mismatches for the other domains will cause Traffic Server to warn and return 403.

Traffic Server will allow a client certificate to be provided for example.com and if it is, Traffic Server will require the certificate to be valid.

sni:
- fqdn: example.com
verify_client: MODERATE
- fqdn: 'foo.com'
verify_client: STRICT
host_sni_policy: PERMISSIVE
- fqdn: '*.yahoo.com'
verify_client: STRICT

Disable outbound server certificate verification for trusted.example.com and require a valid client certificate.

sni:
- fqdn: trusted.example.com
verify_server_policy: DISABLED
verify_client: STRICT

Use FQDN captured group to match in tunnel_route.

sni:
- fqdn: '*.foo.com'
tunnel_route: '$1.myfoo'
- fqdn: '*.bar.*.com'
tunnel_route: '$2.some.$1.yahoo'

FQDN some.foo.com will match and the captured string will be replaced in the tunnel_route which will end up being some.myfoo. Second part is using multiple groups, having bob.bar.example.com as FQDN, tunnel_route will end up being bar.some.bob.yahoo.

SEE ALSO

SNI Routing

COPYRIGHT

2025, dev@trafficserver.apache.org